Lotjd-speakek unit



3 Oct. 23, 1928. 1,688,625

M. A. KENNEDY LOUD SPEAKER UNIT Filed March 26, 1928 0 t: i I

- ATTORNEY Patented Get. 23, 1228.

narra MARZO ALLEN KENNEDY, OF CHICAGO, ILLINOIS, ASSZGNOR TO EDMUND A.RUSSELL, OF CHICAGO, ILLEHOIS.

LOUD-SPEAKER UNIT.

Application filed March 26, 1928. Serial No. 264,938.

This invention relates to loud speaker units for radio receiving sets.

Principal objects of the invention are:

To increase the sensitiveness of loud speaker units of the general typespecified;

To increase the volume and improve the quality of the soundreproduction;

To simplify the construction of the unit;

To obviate the necessity for adjustment of the reed or armature; and

To provide a loud speaker unit which will operate with substantialuniformity.

To effect the objects of the invention, a loud speaker unit embodying myinvention and improvements, comprises the various tures, combinations offeatures and details of construction hereinafter described and claimed.

In the accompanying drawings, in which my invention is fullyillustrated:

Figure 1 is a sectional side view of a loud speaker embodying myinvention and improvements, the section being taken substantially on theline 11 of Fig. 2;

Figure 2 is a bottom plan view from the position 2-2 of Fig 1;

Figure 3 is an enlarged sectional view of the loud speaker unitsubstantially on the line 33 of Fig. 1, the mounting and cone beingomitted; and

Figure 4c is an isometric projection of loud speaker unit.

Describing the invention with particular reference to the drawings, myimproved loud speaker unit, designed as a whole A, comprises a base 1,which may be made of suita ble non-magnetic material and which conveniently can be die cast from suitable nonmagnetic metal.

Mounted on the base 1, and preferably in spaced relation thereto, is ahorseshoe mag net 2, preferably a permanent magnet.

Secured to opposite poles and to opposite sides of said horseshoemagnet, are soft iron plates 3 and 4, which extend inwardly so thattheir unattached ends will be positioned one above the other, andsecured to said plates, respectively, in axial alignment with each otherare electro-magnets 5 and 6. In accordance with usual practice, thewindings of said electr c-magnets are connected in series and theterminals thereof are connected to binding posts 7 and 8, which asshown, are secured to a plate 9 attached to the magnet 1, as aconvenient support, at a desired disthe tance rearwardly from theelectro-magnets 5 and 6, to which the conductor wires 10 for connectingthe loud speaker unit with a radio or other sound receiving set are alsoconnect ed. If the plate 9 is made of material which is an electricalconductor, the binding posts will be insulated therefrom in any usual ordesired manner, as by fibre bushings 11.

The armature of the magnetcommonly known as the ieed consists of a plate12 of resilien metal, preferably soft iron, the end of which remote fromthe electro-magnets is secured b suitable connecting means with theplate 9 and a second plate 13 secured to the opposite side of the magnet1 from said plate 9 and dir ct-ly above it. As shown, said reed orarmature is connected to said plates 9 and 13 by means of clampingscrews 14 which extend thro gh holes in the plate 9 and have threadedenga ement with ioles in the plate 13, inserted over which are spacingsleeves 15, which are so proportioned that when the screws 1-1 aretightened, said reed or armature will be firmly clamped between theadjacent ends of the spacing sleeves 15, the relation being such thatthe free end of said reed or armature will extend between and projectbeyond the electro1nagnets 5 and 6 and as near as may be, cqui-distantfrom the poles thereof, being separate from both thereof by a short airgap.

Secured in the projecting end of the armature or reed 12 is a pin 16 ofsmall diameter, mounted at the upper end of which is a cone 1?, whichmay be made of paper, parchment or like material. The cone 1'?exemplifies any suitable form. of vibrator.

The pin 16 preferably is secured to the reed or armature 11 at adistance of about onehalf an inch from the common axis of the cores ofthe electro-magnets.

Due to the manner of mounting the electromagnets 5 and 6, one above andthe other below the reed or armature 12 with their windings connected inseries, it is obvious that the magnetic fields at opposite sides of saidreed or armature will be of opposite potential, one repelling and theother attracting said reed or armature when said electro-magnets areenergized, and that the resilience of said reed or armature will returnit to normal or neutral positionwholl v or partiallywith va riations inthe strength of the current traversing said electro-magnets. Aparticular advantage due to the characteristic that the electro-magnetsassist instead of oppose each other is that variations in the size ofthe gaps which separate said reed or armature from the poles of theelectro-magnets, respectively, is to a large extent immaterial, thusobviating the necessity for means for adjusting the position of the reedor armature relative to the poles of said eletcro-magnets.

Advantages inherent in my improved loud speaker unit arising from thestructural features described are:

1. Simplicity of construction.

2. Great sensitiveness.

3. Uniform performance.

4. Increased volume.

5. N0 adjustment required; and

6. Greater range of frequencies.

In use, my improved loud speaker unit may be mounted for use upon anysuitable support 18, which may exemplify the wall of a cabinet or othersuitable support. Simple means for thus mounting the instrument consistof screws inserted through holes in the base 1 of the instrument, thelower ends of which have threaded engagement with holes in the support18, sleeves 19 preferably being inserted over said screws between thebase 1 of the instrument and the support 18.

In accordance with usual practice and to prevent access of dust and dirtto the loud speaker unit A, the parts thereof are preferably enclosed ina casing 20, the lower side of which is open and is adapted to besecured to the edges of the instrument base 1, being preferably fittedtightly thereto and resting upon a shoulder thereon. Formed in the topof the casing 20 is a hole 21 through which the. pin 16 extends, saidhole being made sufficiently larger than the pin to insure that said pinwill not contact with the casing at the edges of said hole.

I claim:

1. In a loud speaker unit, the combination of a non-magnetic base, ahorseshoe magnet supported thereon, soft iron plates secured toopposite. poles and opposite sides of said horseshoe magnet theunattached ends of which overlap, electromagnets mounted on adjacentsides of the overlapping ends of said plates, the relation being suchthat the adjacent ends of the cores of said electromagnet will be spacedapart, the windings of said electro-magnets being Connected in series,and a resilient reed secured at one end to a relatively fixed support,the relation being such that the free end of said reed will extend intothe space between the adjacent ends of the cores of the electro-magnets,and a vibrator connected to said reed.

2. In a loud speaker unit, the combination of a non-magnetic base, ahorse-shoe magnet supported thereon, soft iron plates secured toopposite poles of said horse-shoe magnet comprising overlappingportions, electro-magnets mounted on said plates with the adjacent endsof the cores thereof spaced apart, and a resilient reed secured to arelatively fixed support which extends into the space between theadjacent ends of the cores of the electro-magnets, and a vibratorconnected to said reed.

3. A loud speaker unit as specified in claim 1, in which the reedprojects beyond the elec tro-n'iagnets and the vibrator is connected tosaid reed by a pin secured in the reed.

at. A loud speaker unit as specified in claim 1, in which theelectro-magnets are mounted with the axes of their cores in sub stantialalignment.

5. A loud speaker unit as specified in claim 1, in which the gapsbetween the reed and the adjacent ends of the cores of theelectro-magnets, respectively, are normally substantially equal andconstant.

In witness that I claim the foregoing as my invention, I affix mysignature this 22nd day of March, 1928.

MAR-Z0 A. KENNEDY.

